1. Field of the Invention
The present invention relates generally to apparatus and method for communications and more specifically to mobile radio data communications systems.
2. Description of the Related Art
Circuit switching is inefficient for bursty mobile data services such as facsimile (fax), electronic mail (email), and short messaging. First generation cellular systems that provide data communications using circuit switching have difficulty passing modem signals through the audio filters of receivers designed for analog air-interfaces. Inevitably, voice filtering must be deactivated when data is transmitted over first generation cellular networks, and a dedicated data link must be established over the common air-interface. The demand for packet data services has, until recently, been significantly less than the demand for voice services, and first generation subscriber equipment design has focused almost solely on voice-only cellular communications. The cellular digital packet data (CDPD) standard was developed to coexist with the conventional voice-only cellular system.
However, numerous shortcomings exist with CDPD systems. One such shortcoming occurs when a mobile end-station (M-ES) is roaming away from the area covered by its home mobile data intermediate station (MD-IS). Much time, overhead processing and routing resources are expended in forwarding the data to the MD-IS serving the area in which the M-ES is now visiting.
There is accordingly a need for improvements in the system and method for routing digital packet data to a roaming M-ES in a Cellular Digital Packet Data network in order to solve or ameliorate the above-described problem.